This invention relates to a training device for training a user to ensure the correct usage of a pressurised metered dose inhaler (PMDI). In particular, this invention relates to a training device which can be used in training in a way which mimics a PMDI.
Pressurised metered dose inhaler (PMDI) devices are the most popular and widely prescribed devices for respiratory drug delivery, with approximately 500 million manufactured each year.
In such devices, the active ingredient/drug is typically provided in the form of a solution or suspension held in a pressurised canister. Actuation of the canister is typically achieved by depressing the canister towards the body of the device. This causes an interaction between the canister and a valve seat that causes a metered dose to be ejected from the canister, along with a propellant gas (typically a hydrofluoroalkane (HFA) gas). The dose becomes aerosolized and available for inhalation by the patient.
The perception is that these devices are easy to use but this is far from the reality: seemingly simple steps such as coordination of actuation of the canister with inhalation, and inhaling at the appropriate flow rate are often performed incorrectly.
Correct use of PMDIs includes the following procedures: 1) breathing out gently (as far as comfortable); 2) sealing the mouth around the mouthpiece or spacer, breathing in slowly and steadily and then depressing the canister; and 3) continuing to breathe in slowly (preferably for at least 5 seconds) before removing PMDI from mouth.
Incorrect use of PMDIs has been shown to be very common in clinical practice. Numerous trials have demonstrated that a large percentage of patients (>60%) make errors in using PMDIs. Typical errors include depressing the canister before establishing the slow and steady inhalation, and not continuing to inhale for a sufficient length of time after depression of the canister.
When these errors occur, the medication is often not delivered as prescribed contributing to poor asthma control.
New users are typically given instructions on how to use a PMDI but written instructions alone have been found to be insufficient. Ideally, users should be trained in the correct usage of PMDIs (and preferably given revision-training to ensure that correct usage is maintained). It is known to use placebo PMDIs for instructional purposes and demonstration. Placebo PMDIs include a canister (containing propellant gas) in which the active ingredient has been omitted.
There are several known problems with the placebo devices. Firstly, they are not readily available—they are usually sourced through pharmaceutical companies. Secondly, they are costly to manufacture. These two problems can lead to the undesirable re-use of placebo devices in hospital/clinic settings across a significant number of patients (an MDI typically holds up to 200 actuations) despite recommendations for single patient use of both canister and mouthpiece. This, of course, raises concerns about hygiene.
Another problem with the placebo PMDIs is that the propellants used in the canisters have an environmental impact. For example, the propellants in PMDIs for asthma and chronic obstructive pulmonary disease represent approximately 40% of GSK's total carbon footprint. There is also some concern that the propellants may be a contributing factor in paradoxical bronchoconstriction.
A number of aids to help patients with their PMDI use do exist. There are various simple devices such as the 2-Tone Trainer™ (Canday Medical) and FLO-TONE™ pMDI attachment (Clement Clarke International) which provide an audible tone to indicate when the correct inspired air flow rate for drug delivery is achieved. However, the 2-Tone Trainer™ does not provide a realistic training experience since, although it has the appearance of a PMDI, it does not mimic the action of a PMDI and does not provide any training about the timing of canister TM depression. The FLO-TONE pMDI attachment is a spacer for attachment to a placebo or drug PMDI. Therefore it does not avoid the problems associated with the use of propellant gas, or the necessity to use a placebo or drug device during the teaching practice.
A number of more complex devices have also been proposed. These complex devices typically include computer hardware/software/electronics and thus are expensive and not suitable for home use. Some of these complex devices still require the use of a placebo PMDI and thus retain the problems mentioned above.
Accordingly, there remains the need for a training device for training users in the correct usage of a PMDI which is cost effective, suitable for home use, does not require the use of propellant gases, which can easily be cleaned and which can provide guidance on the coordination of inhalation and depression of the drug canister. The present invention aims to meet at least some of these needs.